E3 2014: That Uncharted 4 trailer was made from an in-game engine

Coirrinne Yu works at Naughty Dog for coding animation and graphics. It's safe to say that she knows a thing or do about that Uncharted 4 teaser we saw at the end of Sony's E3 press conference. So when she was asked whether or not it was in-game, she definitely knew the answer: